Remotely excited magnetic nanoparticles and gas–liquid mass transfer in Taylor flow regime

Gas–liquid mass transfer from oxygen Taylor bubbles to liquid in tube was studied using dilute colloidal suspensions of magnetic nanoparticles (MNPs) as the liquid phase. The tube was hosted inside the bore of a tubular two-pole three-phase magnet and the MNPs were remotely excited by subjecting them to different types of magnetic fields. The influence of magnetic field on the liquid side volumetric mass transfer coefficient (kLa) was cast as an enhancement factor with respect to the magnetic field free base case. The repercussions of magnetic field frequency, MNP concentration, tube alignment and gas velocity on this enhancement factor were measured experimentally. Experimental results suggested that spinning nanoparticles under transverse rotating magnetic fields (TRMF) improved mixing in the lubricating film that surrounds Taylor bubbles which reflected in a measurable enhancement of kLa. On the contrary, axial stationary magnetic fields (ASMF) pinned MNPs translating in systematically degraded gas–liquid mass transfer rates whereas axial oscillating magnetic field had no detectable effects on the mass transfer coefficient.

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► MNPs are maneuvered at inaccessible liquid film in Taylor flow using magnetic field.
► Spinning MNPs under RMF transfer momentum to surrounding liquid molecules.
► Magnetically-induced nanoconvection enhances kLa in capillary Taylor flow regime.
► Magnetically pinned MNPs weaken gas–liquid mass transfer in Taylor flow regime.